System and method for generator phase signal monitoring and control

ABSTRACT

A vehicle electrical system comprises a generator and a control device coupled with the generator and operable to protect the generator from catastrophic failure while providing the electrical load in the electrical system with sufficient electrical power. The control device determines a loss of symmetry between two alternating phase signals generated by a first and second phase windings of a single or multiple stator generator. In particular, the control device determines a first and second average values of two of the two or more alternating phase signals and either limits or ceases the total electrical output current of the generator, via a generator output power controller, when the first average value differs from the second average value by a predetermined value. The control device may alternatively be configured to generate an error signal without varying the generator&#39;s total electrical output current even in the event of a malfunction.

REFERENCE TO COMPUTER PROGRAM LISTINGS SUBMITTED ON COMPACT DISK

This specification includes a compact disk appendix, which containscomputer program code listings pursuant to 37 C.F.R. 1.52(e), and ishereby incorporated by reference. The computer codes are in ASCII formatand are as follows:

Creation Creation File Size Date Time (Kilobytes) File Name Jun. 24,2009 11:38 AM 12 CAN-1.H Jun. 24, 2009 11:38 AM 8 DEFINES-1.H Jun. 24,2009 11:38 AM 3 DRIVERS-1.H Jun. 24, 2009 11:38 AM 4 EEPROM-1.H Jun. 24,2009 11:38 AM 7 INIT-1.H Jun. 24, 2009 11:38 AM 4 LIMIT-1.H Jun. 24,2009 11:38 AM 8 REGISTER-1.H Jun. 24, 2009 11:38 AM 6 RTOS-1.H Jun. 24,2009 11:38 AM 7 SENSOR-1.H Jun. 24, 2009 11:38 AM 34 TEST1-1.C Jun. 24,2009 11:38 AM 14 TEST-1.H Jun. 24, 2009 11:38 AM 9 VECTORS-1.H Mar. 20,2009  2:33 PM 120 TEST1.MAP Mar. 20, 2009  2:29 PM 7 DEFINES.H Mar. 20,2009  2:29 PM 35 TEST1.C Jan. 15, 2009 11:19 AM 6 RTOS.H Jan. 15, 200911:06 AM 10 VECTORS.H Jan. 15, 2009 11:05 AM 14 CAN.H Jan. 15, 200911:02 AM 2 DRIVERS.H Jan. 15, 2009 11:01 AM 9 INIT.H Aug. 10, 2007  1:42PM 7 SENSOR.H Aug. 15, 2007 12:59 PM 10 TEST.H Jun. 4, 2004 11:00 AM 2LINKER.PRM Jun. 4, 2004 10:59 AM 7 REGISTER.H Mar. 19, 2004  4:05 PM 4EEPROM.H Jan. 31, 2004  8:15 AM 3 SCRLIMIT.H

COPYRIGHT

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The owner has no objection tothe facsimile reproduction by anyone of the patent disclosure, as itappears in the Patent and Trademark Office files or records, butotherwise reserves all copyright rights whatsoever.

FIELD OF INVENTION

This invention is related to a system and method for monitoring andcontrol of a generator and electrical current in an electrical system.In particular, this invention relates to a control device, including asystem and method, which monitors the phase signals generated by thegenerator's phase windings and controls the output power of thegenerator according to the phase signals. Additionally, the controldevice may operate upon one or more switches to control the magnitudeand direction of electrical current through the electrical systemaccording to the phase signals. The control device may be used inconjunction with the generator for improved monitoring, diagnostics, andcontrol functions. The control device may be used in conjunction with agenerator output power controller to limit or cease a total electricaloutput current.

BACKGROUND

The present invention relates to a control device, including a systemand method, for monitoring a generator's phase signals to control thegenerator's output current and/or electrical current through anelectrical system. In particular, the control device monitors two phasesignals, generated by the generator phase windings, and responses to aloss of symmetry in the phase signals. The control device achieves thisby comparing the two phase signals to one another as opposed topredetermined values. One of the advantages of the present method ofrelative comparison between two phases is that it eliminates the need todetermine other parameters that affect the predetermined values, such asgenerator speed, electrical load, and direction of rotation. It shouldbe noted that the term symmetry refers to the symmetry between differentwaveforms associated with the different phases, not for the positive andnegative parts of an individual waveform associated with each of the twophases as is the case for traditional determination of AC system health.The loss of symmetry is generally an indication of generator malfunctionwhich may damage the generator itself and/or electrical components inthe electrical system. Upon detection of such loss of symmetry, thecontrol device operates to limit or cease the generator output currentvia the generator output power controller and/or control the magnitudeand direction of electrical current through the electrical system via aswitch module. Alternatively, the control device may only generate awarning signal in response to the loss of symmetry.

Electrical systems, such as those implemented in modern vehicles orgenerator sets, include complex electronics and electrical equipment.Such electrical systems are normally comprised of an internal combustionengine and a generator. The engine supplies the generator withmechanical power where it is converted to electrical power. In avehicle, for instance, the generator generates electrical power for thevehicle electrical system when the vehicle's engine is operating. In agenerator set, the engine's mechanical power is converted to electricalpower by the generator which is available via power output connectors.Such electrical systems further include energy storage devices such asbatteries. The batteries and generator can operate either as a load or asource. Whenever the generator is not operating or can not producesufficient electrical power, including the engine start process, thebatteries provide electrical energy to the electrical system. Thegenerator functions as a source of electrical energy after it attains acertain RPM, at which point electrical power is generated by thegenerator and delivered to the batteries and other electrical powerconsuming components within the electrical system.

Ordinarily, the generator includes a voltage regulator that maintainsthe generator voltage at a regulation voltage. Modern generators includea control device that, in addition to regulating the generator voltage,operates to monitor the generator performance in relation with thevehicle electrical and mechanical system. For instance, in a commonlyassigned U.S. Pat. No. 7,466,107 entitled “System and Method forElectric Current and Power Monitoring and Control of a Generator,”hereby incorporated by reference in its entirety, a control device incombination with a generator was disclosed where the control deviceoperated to limit or cease the generator output current in response toan overload detected by measuring a voltage drop across a conductorembedded in the generator. The control device further operated tocontrol the generator output current as a function of batterytemperature, battery type, battery voltage, and the ratio between theRPMs of the engine and generator. Also, see Jabaji, U.S. Pat. No.7,276,804 where a voltage regulator has been disclosed which, inaddition to regulating the generator output voltage, operates to discernand respond to regulator, generator, and vehicle electrical systemoperation and malfunctions; Becker et al., U.S. Pat. No. 6,184,661,where the control device operates to limit the generator output power inorder to protect the engine from excessive generator torque; and Jabaji,U.S. Pat. No. 5,907,233, where the control device monitors the AC signalgenerated by the stator windings and, in the absence of the AC signal,removes the field coil current in order to protect the battery fromexcessive drain.

In order to provide supplemental monitoring, diagnostics, and controlfunctions, the control device may monitor the signals generated by thephase windings and control either or both the generator output current,and the magnitude and direction of electrical current through theelectrical system. It should be noted that the present invention is notlimited to sinusoidal, square, quasi-square, or any other form ofsymmetric waveform. A typical generator comprises stator windings thatproduce the generator output current via a varying magnetic field.Multi-phase generators have multiple stator windings that are connectedvia Δ (delta) or Y arrangement, known to skilled artisans. Each phasecarries a proportional amount of the total generator output current. Forinstance in a 3-phase generator, each phase carries approximately ⅓ ofthe total generator output current, assuming the phase windings areidentical.

Generators produce electrical power via their phase windings. In amulti-phase generator, the total electrical power generated by thegenerator is the sum of the electrical power generated by the individualphase windings. Accordingly, monitoring their performance can be usefulin determining the performance of the generator. The signals generatedby the phase windings can be compared to ascertain fault conditionsassociated with the generator. A loss of symmetry in the phase signalsmost likely is an indication of a malfunctioning generator. As statedabove, the term symmetry refers to the symmetry between differentwaveforms associated with the different phases, not for the positive andnegative parts of an individual waveform associated with each of the twophases as is the case for traditional determination of AC system health.Specifically, the loss of symmetry could be due to shorted phasewindings and/or one or more faulty rectifying diodes. When suchmalfunctions occur, it is desirable to control the output current of thegenerator and/or the magnitude and direction of the electrical currentin the electrical system.

In general, a shorted phase winding produces such excessive temperaturesthat the event can lead to total generator failure. The shorted phasecould be due to a short between windings, within winding turns,alternator casing, etc. The rate at which the temperature of the phasewindings reaches the point of catastrophic failure depends on theelectrical load being delivered by the generator. When the generator isoperating at or near full load, these extreme temperatures occur in arelatively short period of time. Such catastrophic temperatures could bedelayed or avoided if the generator output current is limited or ceased.Preferably, upon detection of a shorted phase winding, it would bedesirable to turn off the generator output current before it undergoesirreversible damage. However, there are many situations in which theelectrical system solely depends on the generator output power toprovide electrical power to the electrical devices within the electricalsystem. Under these circumstances, it is desirable to limit thegenerator output current to avoid the extreme temperatures whiledelivering enough power to vital components within the electrical systemuntil the generator is repaired. Additionally, a warning or a controlsignal can be generated to either warn the operator to reduce theelectrical load by manually switching off certain electrical components,or to apply the control signal to a switch module to automaticallydisconnect unnecessary electrical loads.

SUMMARY

The present invention discloses a vehicle electrical system comprising agenerator and a control device. The generator comprises two or morephase windings associated with one or more stators. The phase windingsoperate to generate two or more alternating phase signals. The controldevice is responsive to the two or more phase signals and operate todetermine a first and second average values of two of the two or morealternating phase signals, and to at least one of limit and cease atotal electrical output current of the generator, via a generator outputpower controller, when the first average value differs from the secondaverage value by a predetermined value. Preferably, the two or morealternating phase signals comprise two or more alternating phase voltagesignals. In another instance, the two or more alternating phase signalscomprise two or more alternating phase current signals. Preferably, thetwo alternating phase signals are generated by two different phasewindings associated with two different stators. Preferably, thegenerator output power controller comprises at least one of a voltageregulator, a field coil, and a semiconductor switch. Preferably, thepredetermined value is substantially between 1% and 5%.

In another aspect, a vehicle electrical system comprising a generatorand a control device is disclosed. The generator comprises two or morephase windings associated with one or more stators which generate twomore alternating phase signals. The control device is responsive to thetwo or more phase signals and operate to determine a first and secondaverage values of two of the two or more alternating phase signals, andto at least one of limit and cease a total electrical output current ofthe generator, via a generator output power controller, when the firstaverage value differs from the second average value by a predeterminedvalue. Preferably, the control device is further operative to generatean error signal indicative of a fault condition when the first averagevalue differs from the second average value by the predetermined value.

In another aspect, a vehicle electrical system comprising a generatorand a control device is disclosed. The generator comprises two or morephase windings associated with one or more stators which generate twomore alternating phase signals. The control device is responsive to thetwo or more phase signals and operate to determine a first and secondaverage values of two of the two or more alternating phase signals, andto at least one of limit and cease a total electrical output current ofthe generator, via a generator output power controller, when the firstaverage value differs from the second average value by a predeterminedvalue. Preferably, the control device further comprises a voltageregulator capable of maintaining an output voltage of the generatorsubstantially at a regulation voltage.

In another aspect, a method for controlling a vehicle electrical systemincluding a generator is disclosed. The method comprises generating twoor more alternating phase signals via two or more phase windingsassociated with one or more stators included in the generator,determining a first and second average values of two of the two or morealternating phase signals, and at least one of limiting and ceasingtotal electrical output current of the generator, via a generator outputpower controller, when the first average value differs from the secondaverage value by a predetermined value.

In another aspect, a method for controlling a vehicle electrical systemincluding a generator is disclosed. The method comprises generating twoor more alternating phase signals via two or more phase windingsassociated with one or more stators included in the generator,determining a first and second average values of two of the two or morealternating phase signals, and at least one of limiting and ceasingtotal electrical output current of the generator, via a generator outputpower controller, when the first average value differs from the secondaverage value by a predetermined value. Preferably, the method furtherincludes generating an error signal indicative of a fault condition whenthe first average value differs from the second average value by thepredetermined value.

In another aspect, a method for controlling a vehicle electrical systemincluding a generator is disclosed. The method comprises generating twoor more alternating phase signals via two or more phase windingsassociated with one or more stators included in the generator,determining a first and second average values of two of the two or morealternating phase signals, and at least one of limiting and ceasingtotal electrical output current of the generator, via a generator outputpower controller, when the first average value differs from the secondaverage value by a predetermined value. Preferably, the method furtherincludes maintaining an output voltage of the generator substantially ata regulation voltage via a voltage regulator.

In another aspect, a control device for a generator is disclosed. Thegenerator comprises two or more phase windings associated with one ormore stators. The two or more phase windings operate to generate two ormore alternating phase signals. The control device comprises a processorcoupled with two or more phase windings and a generator output powercontroller. The processor includes a programming code operable on theprocessor. The processor is configured to measure the two or morealternating phase signals via two or more lines, determine a first andsecond average values of two of the two or more alternating phasesignals, and apply a control signal to the generator output powercontroller to at least one of limit and case a total electrical outputcurrent of the generator, via a control line, when the first averagevalue differs from the second average value by a predetermined value.Preferably, the two or more alternating phase signals comprise two ormore alternating phase voltage signals wherein each alternating phasevoltage signal is measured between one end of the corresponding phasewinding and ground. In another instance, each of the alternating phasevoltage signals is measured between one end of the corresponding phasewinding and a reference point at a DC voltage as is the case in anisolated ground configuration. Preferably, the two alternating phasesignals are generated by two different phase windings associated withtwo different stators. Preferably, the generator output power controllercomprises at least one of a voltage regulator, a field coil, and asemiconductor switch. Preferably the processor is configured todetermine the first and second average values by filtering the two ormore alternating phase signals and calculating a first and second DCvalues from two of the two or more filtered alternating phase signals.Preferably, the processor is configured to apply a phase modulatedsignal to limit the total electrical output current of the generator.Preferably, the processor is configured to apply a step signal to ceasethe total electrical output current of the generator. Preferably, theprocessor is configured to apply a control signal to the generatoroutput power controller to at least one of limit and cease a totalelectrical current of the generator, via the control line, when a ratiobetween the first and second average values is outside of apredetermined range. Preferably, the predetermined range issubstantially between 95% and 105%.

In another aspect, a control device for a generator is disclosed. Thegenerator comprises two or more phase windings associated with one ormore stators. The two or more phase windings operate to generate two ormore alternating phase signals. The control device comprises a processorcoupled with two or more phase windings and a generator output powercontroller. The processor includes a programming code operable on theprocessor. The processor is configured to measure the two or morealternating phase signals via two or more lines, determine a first andsecond average values of two of the two or more alternating phasesignals, and apply a control signal to the generator output powercontroller to at least one of limit and case a total electrical outputcurrent of the generator, via a control line, when the first averagevalue differs from the second average value by a predetermined value.Preferably, the processor is further configured to generate an errorsignal indicative of a fault condition, via a communication line, whenthe first average value differs from the second average value by thepredetermined value.

In another aspect, a control device for a generator is disclosed. Thegenerator comprises two or more phase windings associated with one ormore stators. The two or more phase windings operate to generate two ormore alternating phase signals. The control device comprises a processorcoupled with two or more phase windings and a generator output powercontroller. The processor includes a programming code operable on theprocessor. The processor is configured to measure the two or morealternating phase signals via two or more lines, determine a first andsecond average values of two of the two or more alternating phasesignals, and apply a control signal to the generator output powercontroller to at least one of limit and case a total electrical outputcurrent of the generator, via a control line, when the first averagevalue differs from the second average value by a predetermined value.Preferably, the processor is further configured to measure an outputvoltage of the generator, via an output-voltage line, and to vary a dutycycle of the generator output power controller, via the control line, sothat the output voltage is substantially equal to a regulation voltage.

In another aspect, a method for controlling a generator is disclosed.The generator comprises two or more phase windings associated with oneor more stators. The two or more phase windings operate to generate twoor more alternating phase signals. The method comprises measuring thetwo or more alternating phase signals, determining a first and secondaverage values of two of the two or more alternating phase signals, andapplying a control signal to a generator output power controller to atleast one of limit and case a total electrical output current of thegenerator, via a control line, when the first average value differs fromthe second average value by a predetermined value. Preferably, themethod of measuring the two or more alternating phase signals, via twoor more lines, comprises measuring two or more alternating phase voltagesignals between one end of the corresponding phase winding and ground.In an isolated ground system, the measurements are made between thephase and a reference point at a DC voltage. Preferably, the method ofdetermining a first and second average values of two of the two or morephase signals comprises filtering the two or more alternating phasesignals and calculating a first and second DC values from two of the twoor more filtered alternating phase signals. Preferably, the method ofapplying a control signal to the generator output power controllercomprises applying a phase modulated signal to limit the totalelectrical output current of the generator. Preferably, the method ofapplying a control signal to the generator output power controllercomprises applying a step signal to cease the total electrical outputcurrent of the generator. Preferably, the method of applying a controlsignal to the generator output power controller to at least one of limitand cease a total electrical output current of the generator, via thecontrol line, comprises applying the control signal when a ratio betweenthe first and second average values is outside of a predetermined range.

In another aspect, a method for controlling a generator is disclosed.The generator comprises two or more phase windings associated with oneor more stators. The two or more phase windings operate to generate twoor more alternating phase signals. The method comprises measuring thetwo or more alternating phase signals, determining a first and secondaverage values of two of the two or more alternating phase signals, andapplying a control signal to a generator output power controller to atleast one of limit and case a total electrical output current of thegenerator, via a control line, when the first average value differs fromthe second average value by a predetermined value. Preferably, themethod further comprises generating an error signal indicative of afault condition, via a communication line, when the first average valuediffers from the second average value by the predetermined value.

In another aspect, a method for controlling a generator is disclosed.The generator comprises two or more phase windings associated with oneor more stators. The two or more phase windings operate to generate twoor more alternating phase signals. The method comprises measuring thetwo or more alternating phase signals, determining a first and secondaverage values of two of the two or more alternating phase signals, andapplying a control signal to a generator output power controller to atleast one of limit and case a total electrical output current of thegenerator, via a control line, when the first average value differs fromthe second average value by a predetermined value. Preferably, themethod further comprises measuring an output voltage of the generator,via an output-voltage line, and varying a duty cycle of the generatoroutput power controller, via the control line, so that the outputvoltage is substantially equal to a regulation voltage.

In another aspect, a control device for a generator is disclosed. Thegenerator comprises two or more phase windings associated with one ormore stators. The two or more phase windings operate to generate two ormore alternating phase signals. The control device comprises a processorcoupled with two or more phase windings and a generator output powercontroller. The processor includes a programming code operable on theprocessor. The processor is configured to measure the two or morealternating phase signals via two or more lines, determine a first andsecond average values of two of the two or more alternating phasesignals, and generate an error signal indicative of a fault condition,via a communication means, when the first average value differs from thesecond average value by a predetermined value. Preferably, thecommunication means comprises a communication terminal, coupled with acomputer system, capable of transmitting/receiving a communicationsignal indicative of the fault condition. Preferably, the communicationmeans comprises a light emitting diode, generating a flashing lightpattern indicative of the fault condition.

In another aspect, a method for controlling a generator is disclosed.The generator comprises two or more phase windings associated with oneor more stators. The two or more phase windings operate to generate twoor more alternating phase signals. The method comprises measuring thetwo or more alternating phase signals, determining a first and secondaverage values of two of the two or more alternating phase signals, andgenerating an error signal indicative of a fault condition, via acommunication means, when the first average value differs from thesecond average value by a predetermined value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a vehicle electrical system comprising agenerator, a voltage regulator, electrical load, and control deviceaccording to a preferred embodiment.

FIG. 2 shows a schematic diagram of a vehicle electrical systemcomprising a dual-stator generator and the associated phase windings,rectifier assemblies, electrical load, and a control device operative onthe generator's output power controller to limit and/or cease thegenerator's output power according to a preferred embodiment.

FIG. 3 shows a schematic diagram of a control device, including aprocessor, that measures two phase signals and controls the generator'sfield coil duty cycle in response to the phase signals while regulatingthe generator's output voltage and communicating the generator's statusvia an LED and I/O port according to a preferred embodiment.

FIG. 4 is a flow diagram of one preferred method of monitoring andcontrol of the generator in the vehicle electrical system of FIGS. 1 and2, further illustrating the operation of the control device andutilization of the phase signals generated by the phase windings.

FIG. 5 is a flow diagram of one preferred method of monitoring andcontrol of the generator in the vehicle electrical system of FIGS. 1 and2, specifically illustrating the processing steps performed by thecontrol device to ascertain whether to limit or cease the generator'stotal electrical output current.

FIG. 6 is a flow diagram of one preferred method of monitoring andcontrol of the generator in the vehicle electrical system of FIGS. 1 and2 that maybe implemented on a processor, included in the control device,further detailing the conditions under which the generator's totaloutput current is either limited or ceased.

FIG. 7 is a flow diagram of one preferred method of monitoring andcontrol of the generator in the vehicle electrical system of FIGS. 1 and2 that maybe implemented on a processor, included in the control device,further detailing the conditions under which the generator's totaloutput current is either limited or ceased.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 depicts a block diagram of a preferred embodiment of a vehicleelectrical system 100, including a generator 106, a voltage regulator102, electrical load 110, communication means 112, and a control device118. The control device 118 is connected to and in communication withthe generator 106 via lines 116, 120, and 122. The voltage regulator 102operates to maintain the generator output voltage at a constant voltageas the speed of the generator 106 and electrical load 110 vary. Theelectrical load 110 represents electrical loads by electrical componentswhich may comprise a heating element, an air conditioning unit, acompressor, a cooling fan, headlights, a battery, or a pump, to name afew examples. As these electrical loads are applied and removed from thegenerator 104, the voltage regulator 102 varies the output power of thegenerator 106, via the generator's output power controller (not shown),so as to meet the electrical power requirement of the electrical load110.

In one embodiment, the generator 106 is a brushless alternator havingtwo or more phase windings (not shown) associated with one or morestator windings (not shown). The generator 106 further includes a fieldcoil (not shown) that generates a magnetic field when a field currentpasses through the field coil. The magnetic field interacts with the oneor more stator windings in the generator (not shown), inducing voltageacross the stators which, in turn, produce the generator output currentthrough line 108 for consumption by the electrical load 110. The voltageregulator 102 is coupled with the generator field coil via line 104 andoperates to regulate the system voltage at a regulation voltage, forinstance 28 V, by switching on/off the field coil, thereby, varying theaverage value of the field current.

According to a one embodiment, the voltage regulator 102 comprises aswitch to accomplish this. In one instance, the switch is disposedbetween one end of the field coil and output terminal of the generator106. The voltage regulator 102 senses the output voltage of thegenerator 106 and applies a control signal, via line 104, to switchon/off the switch to maintain the system voltage at the regulationvoltage.

According to another embodiment, the voltage regulator 102 comprises twoswitches to control the output power of the generator 106 and provideover voltage protection. The first switch is disposed between one end ofthe field coil and a voltage source, such as a battery (not shown), anda second switch is disposed between the other end of the field coil andthe voltage source. The voltage regulator 102 senses the output voltageof the generator 106 and applies a control signal to switch on/off thefirst switch to maintain the system voltage at the regulation voltage,and applies another control signal to switch off the second switch inresponse to a generator output voltage that is above a threshold valuefor a predetermined time interval. Following this over voltage conditionand upon a system reset, the regulator switches on the second switch tocontinue normal operation. In this two-switch configuration, the voltageregulator 102 uses the first switch to regulate the system voltage atthe regulation voltage, and the second switch to further prevent overvoltage conditions that may occur when an electrical load is suddenlydisconnected.

In addition to power control and over voltage protection of thegenerator 106, afforded by the regulator 102, additional protection andcontrol can be achieved by monitoring the two or more phase windings ofthe generator 106. The control device 118 is coupled with two phasewindings via lines 116 and 122. The control device 118 is furthercoupled with the generator output power controller, in this case thefield coil of the generator 106. The two phase windings generate twoalternating phase signals that, under normal conditions, produce nearlythe same average values, DC1 and DC2. The control device 118 determinesthese average values and may limit or cease the total electrical currentof the generator 106, via line 120, when DC1 differs from DC2. It shouldbe noted that the present invention is not limited to measurements ofsinusoidal, square, quasi-square, or any other form of symmetricwaveform. It is important to note that the control device 118 comparesDC1 to DC2 as opposed to predetermined values. The advantage is that iteliminates the need to determine other parameters that affect thepredetermined values, such as generator speed, electrical load, anddirection of rotation. It is this loss of symmetry that is detected andused to control the total output current of the generator 106. It shouldbe noted that the term symmetry refers to the symmetry between differentwaveforms associated with the different phases coupled with the lines116 and 122, not for the positive and negative parts of an individualwaveform associated with each of the two phases as is the case fortraditional determination of AC system health.

This loss of symmetry between DC1 and DC2 indicates that the generator106 is malfunctioning. Depending on the amount of symmetry loss, thecontrol device 118 limits or ceases the generator's output current. Ifthe loss of symmetry is outside of a first range, the control device 118limits the total electrical output current of the generator 106. If theloss of symmetry is outside of a second range, the control device 118ceases the total electrical output current of the generator 106. Thecontrol device 118 achieves this by controlling the generator outputpower controller.

According to the embodiment depicted in FIG. 1, the control device 118utilizes line 120 to control the electrical current passing through thefield coil of the generator 106. It should be clear to artisans ofordinary skill that the control device 118 and voltage regulator 102have been so configured so that the control device 118 has the firstpriority control of the field coil over that of the voltage regulator102. In other words, the control device 118's control of the field coilmay not be interrupted by the voltage regulator 102 but the latter'scontrol may be interrupted by the former. In an alternative embodiment,the control device 118 may be configured to further function as avoltage regulator, eliminating the need for a separate voltage regulatorsuch as the voltage regulator 102.

The option to limit the generator's total electrical output current inlight of a potential malfunction is that it allows the generator 106 toprovide what power it can to the electrical load 110 until the vehicleis repaired. In addition to controlling the total electrical outputcurrent of the generator 106, the control device 118 utilizes line 114to communicate the loss of symmetry to the communication means 112. Thecommunication means 112 may be a light emitting diode, a vehiclecomputer system, or the vehicle's display panel.

FIG. 2 depicts a schematic diagram of the electrical connections betweenthe various components within the vehicle electrical system 100 of FIG.1 according to a preferred embodiment. A generator, such as thegenerator 106, comprises a generator output power controller 214 such asa field coil, two three-phase stator windings 202 and 230, and twofull-wave rectifier circuits 206 and 248. The first stator 202 iscomprised of three phase windings 204, 258, and 260. The phase windings204, 258, and 260 generate three alternating phase signals on lines 254,256, and 252, respectively. Such phase signals generally are notsinusoidal, square, quasi-square, or any other form of symmetricwaveforms. The second stator 230 is comprised of three phase windings232, 236, and 240. The phase windings 232, 236, and 240 generate threealternating phase signals on lines 242, 246, and 238, respectively. Thegenerator 106 produces electrical current at its output 210, through anelectrical load 212, to ground at 216. The electrical load 212represents one or more electrical loads by electrical components such asthose mentioned above. A control device 224 is coupled with the firstand second stator windings 202 and 230 via lines 228 and 234. Accordingto this embodiment, the control device 224 measures the alternatingphase signals generated by the phase winding 204 and 240 of the firstand second stator windings 202 and 230, respectively. The control device224 is further coupled with the generator output power controller 214via a line 218 and communication means, LED 220 and I/O Port via lines222 and 226.

In this configuration as depicted in FIG. 2, however, the control device224 also operates as a voltage regulator eliminating the need for aseparate voltage regulator such the voltage regulator 102, FIG. 1. Thecontrol device 224 regulates the output voltage of the generator 106 bymeasuring its output voltage via an output voltage line 262 and varyinga duty cycle of the generator output power controller 214 by applying acontrol signal via the line 218. In addition to maintaining the outputvoltage of the generator 106 at a regulation voltage, the control device224 operates to determine a first and second average values, DC1 andDC2, of two of the alternating phase signals generated by two of thephase windings 204, 258, 260, 232, 236, and 240. It limits or ceases atotal electrical output current of the generator 106 in response to aloss of symmetry between the first and second average values DC1 and DC2by applying a control signal to the generator output power controller214 via the line 218, when the first average value DC1 differs from thesecond average value DC2 by a predetermined value. The term symmetryrefers to the symmetry between two different waveforms associated withtwo different phases amongst phase windings 204, 258, 260, 232, 236, and240, not for the positive and negative parts of an individual waveformassociated with each of the phases as is the case for traditionaldetermination of AC system health.

The generator 106, as represented by the generator output powercontroller 214, two three-phase stator windings 202 and 230, and twofull-wave rectifier circuits 206 and 248, is coupled with the electricalload 212. According to this embodiment, the generator output powercontroller 214 is a field coil which establishes a magnetic field whencurrent passes through it as known to artisans of ordinary skill. Thecontrol device 224 controls the amount of electrical current that passesthrough the field coil. The generator 106 may be a brushless alternator.For a dual stator brushless alternator, as in this embodiment, a rotoris used as a means to vary the magnetic field through the statorwindings 202 and 230, thereby creating an alternating current that isrectified via the two full-wave rectifier circuits 206 and 248. Therectified current is then fed to the electrical load 212.

The generator 106 is ordinarily used in a vehicle and thus subjected toshock and vibration. The generator 106 is further subjected to highambient temperatures during operation. These conditions may give rise tophase winding and/or rectifier failure. Such failures affect thealternating current through the phase windings 204, 258, 260, 240, 236,and 232. During normal operating conditions, the average values of thealternating currents through these phase windings are nearly the same.When a failure of one of the phase windings, such as a shorted phase orrectifier diode, occurs the average values change accordingly. It shouldbe noted that the present invention is independent of the normal changesin average waveform value associated with load surge, load dump,overload, soft start, and the like. The control device 224 mayselectively limit or cease the field current through the field coil 214based on the amount of change which is discussed in more detail below.

FIG. 3 is a schematic diagram of a control device, such as the controldevice 224, including a processor 302. The control device 224 utilizesthe processor 302 to measure alternating phase signals, generated by twophase windings 306 and 308, to measure an output voltage of a generatoroutput terminal 310, and to vary the field current through a field coil320 via switch 322. The processor 302 is also coupled with an I/O bus328 and LED 314, via lines 326 and 316, respectively to indicate theoperating status of the phases 306 and 308. The processor 302 may beanalog or digital such as a microprocessor. In one preferred embodiment,the microprocessor is a 68HC08 processor having internal flash memoryavailable from Freescale of Scottsdale, Ariz. It is contemplated thatthe processor may be a combination of individual discrete or separateintegrated circuits packaged in a single housing or it may be fabricatedin a single integrated circuit. The switch 322 may be a semiconductorswitch.

The processor 302 is coupled with two phase windings 306 and 308 vialines 304 and 318. The phase windings 306 and 308 generate alternatingphase voltage signals on the lines 304 and 318 whose DC values arenearly identical during normal operating conditions. According to oneembodiment, the processor 302 measures the alternating phase voltagesignals across one end of the phase winding 306, 308 and ground. Theprocessor 302 obtains average values DC1 and DC2 of the alternatingphase voltage signals. According to a preferred embodiment, theprocessor 302 filters the alternating phase voltage signals prior todetermining the average values. A low pass digital filter known toartisans of ordinary skill may be utilized. The processor 302 uses theswitch 322 to vary the field current through the field coil 320 inresponse to a loss of symmetry between the average values DC1 and DC2.The term symmetry refers to the symmetry between two different waveformsassociated with phases 306 and 308, not for the positive and negativeparts of an individual waveform associated with each of the phases 306and 308. The loss of symmetry may be manifested in different ways, twoof which are described in more detail below. Depending on the level ofdiscrepancy between DC1 and DC2, the processor 302 either limits orceases the field current through the field coil 322 so as to limit orcease the total electrical output current of the generator 106. If thedifference is above a threshold, the processor 302 stops all fieldcurrent through the field coil 320 by applying a step signal to theswitch 322, thereby, ceasing the total electrical output current of thegenerator 106. If the difference is between a predetermined range,according to one embodiment, the processor 302 applies a phase modulatedsignal to the switch 322 so as to proportionally vary the field currentthrough the field coil 320, thereby, limiting the total electricaloutput current of the generator 106.

The processor 302 may also communicate such fault conditions visually orthrough the vehicle computer system utilizing LED 314 and I/O bus 328via the lines 316 and 326. According to one preferred embodiment, theprocessor 302 neither limits nor ceases the total electrical outputcurrent of the generator 106 but instead utilizes one or more of thecommunication means 314 and/or 328 to generate an error signalindicative of the fault conditions without affecting the generatoroutput power in any way.

The processor 302 further measures the output voltage of the generator106, at the generator output voltage terminal 310 via the line 312.According to this embodiment, the processor 302 also operates as avoltage regulator by maintaining the generator output voltage at aregulation voltage. The processor 302 uses the same switch 322 to varythe field current through the field coil 320 in order to regulate thegenerator output voltage.

FIG. 4 is a flow diagram 400 of one preferred method of operation of thevehicle electrical system of FIG. 1. According to this embodiment, themethod comprises generating two or more alternating phase signals viatwo or more phase windings associated with one or more stators includedin the generator 106 at 402. In general, such phase signals are notsinusoidal, square, quasi-square, or any other form of symmetricwaveforms. A first and second average values of two of the two or morealternating phase signals, such as DC1 and DC2 described above, aredetermined at 406, via the control device 118. DC1 and DC2 are comparedto each other and a total electrical output current of the generator 106is either limited or ceased via a generator output power controller,such as the field coil 320 in FIG. 3, when DC1 differs from DC2 by apredetermined value at 410. The method further includes generating anerror signal via a communication means 112 at 414. According to thispreferred embodiment, the method further includes regulating the outputvoltage of the generator 106 at a regulation voltage via the voltageregulator 102 at 418. As described above, the control device 118 can beconfigured to operate as a voltage regulator eliminating the need for aseparate voltage regulator such as the voltage regulator 102. Also asdescribed above, the method can be modified to eliminate step 410whereby the control device 118 only generates an error signal indicativeof a fault condition without limiting or ceasing the total electricaloutput current of the generator 106.

FIG. 5 is a flow diagram 500 of one preferred method of operation of thecontrol device of FIGS. 1 or 2 further illustrating the operation of aprocessor included in the control device such as the processor 302 ofFIG. 3. The method includes measuring two or more alternating phasevoltage signals between one end of the corresponding phase windings andground at 502. According to this preferred embodiment, the processor 302is a microprocessor and the alternating phase voltage signals generatedby the two phases 306 and 308 are digitized using an analog to digitalconvertor included in the microprocessor 302. Preferably, the analogsignals are first filtered via a low pass analog filter to avoidaliasing before the signals are digitized by said analog to digitalconvertor. The digitized signals are then filtered, preferably using alow pass digital filter to illiminate noise at 506. Each of the filtereddigital signals are then averaged and a first and second DC values, DC1and DC2, are obtained at 506. The microprocessor 302 applies a phasemodulated signal at 510 to limit the total electrical output current ofthe generator 106 if DC1/DC2 is outside of a range between R_(LL) andR_(LH). The microprocessor 302 applies the phase modulated signal to theswitch 322 via the line 324 which in turn reduces the duty cycle of thefield current through the field coil 320. If DC1/DC2 is outside of arange between R_(CL) and R_(CH) the microprocessor 302 applies a stepsignal to the switch 322 to turn off the field current through the fieldcoil 320 ceasing the total electrical output current of the generator106 at 514.

FIG. 6 is a flow diagram 600 of one preferred method of operation of thecontrol device of FIG. 1 or 2 further illustrating the implementation ofa programming code in a processor such as the processor 302 of FIG. 3.Upon power up at 602, the processor 302 measures a first alternatingphase voltage signal from a first phase at 606. The processor 302 thenmeasures a second alternating phase voltage signal from a second phase,belonging to the same or a different stator, at 610. The processor 302performs digital filtering operation on the two phase voltage signals at614 and computes two DC values, DC1 and DC2, from the filtered signalsat 618. DC1 and DC2 are compared to one another by computing the ratioDCR=DC1/DC2 at 622. It should be clear to artisans of ordinary skillthat the ratio DCR could as well be computed by dividing DC2 by DC1.Consequently, there is no preference for any one phase winding in thesecalculations. DCR is then compared to a range between R_(LL) and R_(LH).If DCR is within this range, i.e. normal conditions, the processor 302branches at 642, communicates its status at 644, and branches at 646 tomeasure another set of alternating phase voltage signals. However, ifDCR is outside of the range between R_(LL) and R_(LH), i.e. malfunction,then the processor 302 branches at 628 to perform another comparison at630. At this step, the processor 302 determines the severity of the lossof symmetry between phase one and phase two, i.e., symmetry between twodifferent waveforms associated with phase one and phase two, not for thepositive and negative parts of an individual waveform associated witheach of the phase one and phase two as is the case for traditionaldetermination of AC system health. Specifically, if DCR is within therange between R_(CL) and R_(CH), the processor branches at 636 to limitthe generator's total output current. This is accomplished by applying aphase modulated signal with a duty cycle (D) according to the value ofDCR at 640. According to one embodiment, the duty cycle D may beobtained from a look up table 648. The processor 302 also communicatesthe status via the I/O bus 328 and turns blue the LED 314. If DCR isoutside the range between R_(CL) and R_(CH), the processor branches at632 to cease the generator's total output current which is accomplishedby applying a step signal at 634. The processor 302 also communicatesthe status via the I/O bus 328 and turns red the LED 314. In either caseof limiting or ceasing, the processor 302 branches at 646 or 638 tomeasure another set of alternating phase voltage signals.

FIG. 7 is a flow diagram 700 of one preferred method of operation of thecontrol device of FIG. 1 or 2 further illustrating anotherimplementation of a programming code in the processor 302. Inparticular, the present implementation involves a different way ofevaluating the loss of symmetry between the two phases. Furthermore, asdiscussed above, in the present embodiment the processor 302 alsooperates as a voltage regulator.

Upon power up at 702, the processor 302 measures the generator outputvoltage at 706 and regulates the generator output voltage at 710.Similar to the embodiment described above in FIG. 6, the processor 302measures a first alternating phase voltage signal from a first phase at714 and a second alternating phase voltage signal from a second phase,belonging to the same or a different stator, at 718. The processor 302performs digital filtering operation on the two phase voltage signals at722 and computes two DC values, DC1 and DC2, from the filtered signalsat 726. DC1 and DC2 are compared to one another by computing the ratioDCR=|DC1−DC2|/DC1 at 730. It should be clear to artisans of ordinaryskill that the ratio DCR could as well be computed by subtracting DC1from DC2 and dividing the result by DC2. Consequently, there is nopreference for any one phase winding in these calculations. DCR is thencompared to a range between 0 and R_(LL). If DCR is within this range,i.e. normal conditions, the processor 302 branches at 750, communicatesits status at 752, and branches at 754 to measure the generator outputvoltage at 706. However, if DCR is outside of the range between 0 andR_(LL), i.e. malfunction, then the processor 302 branches at 736 toperform another comparison at 738. At this step, the processor 302determines whether to limit or cease the generator's total outputcurrent depending on the severity of the loss of symmetry between phaseone and phase two. Specifically, if DCR is within the range betweenR_(LL) and R_(LH), the processor 302 branches at 744 to limit thegenerator's total output current. This is accomplished by applying aphase modulated signal with a duty cycle (D) according to the value ofDCR at 748. According to one embodiment, the duty cycle D may beobtained from a look up table 756. The processor 302 also communicatesthe status via the I/O bus 328 and turns blue the LED 314. If DCR isoutside the range between R_(LL) and R_(LH), the processor 302 branchesat 740 to cease the generator's total output current which isaccomplished by applying a step signal at 742. The processor 302 alsocommunicates the status via the I/O bus 328 and turns red the LED 314.In either case of limiting or ceasing, the processor 302 branches at 754or 746 to measure the generator's output voltage at 706.

The foregoing discloses a vehicle electrical system comprising agenerator and a control device that monitors the generator phasewindings and selectively limits or ceases the generator's totalelectrical output current when a loss of symmetry between two such phasewindings are detected. It should be clear to an artisan of ordinaryskill that the term symmetry refers to the symmetry between differentwaveforms associated with the different phases, not for the positive andnegative parts of an individual waveform associated with each of the twophases as is the case for traditional determination of AC system health.In particular, when the loss of symmetry is too severe, the controldevice ceases the generator's total electrical output current. However,if the loss of symmetry is within an acceptable range, the controldevice limits the generator's total electrical output current in aneffort to provide electrical power to the vehicle electrical load whilepreventing irreversible damage to the generator.

The foregoing explanations, descriptions, illustrations, examples, anddiscussions have been set forth to assist the reader with understandingthis invention and further to demonstrate the utility and novelty of itand are by no means restrictive of the scope of the invention. It is thefollowing claims, including all equivalents, which are intended todefine the scope of this invention.

1. A vehicle electrical system comprising: (a) a generator comprisingtwo or more phase windings associated with one or more stators, said twoor more phase windings operative to generate two or more alternatingphase signals; and (b) a control device responsive to the two or morealternating phase signals and operative to determine a first and secondaverage values of two of the two or more alternating phase signals, andto at least one of limit and cease a total electrical output current ofthe generator, via a generator output power controller, when the firstaverage value differs from the second average value by a predeterminedvalue.
 2. The system of claim 1, wherein the two or more alternatingphase signals comprise two or more alternating phase voltage signals. 3.The system of claim 1, wherein the two or more alternating phase signalscomprise two or more alternating phase current signals.
 4. The system ofclaim 1., wherein the two alternating phase signals are generated by twodifferent phase windings associated with two different stators.
 5. Thesystem of claim 1, wherein the generator output power controllercomprises at least one of a voltage regulator, a field coil, and asemiconductor switch.
 6. The system of claim 1, wherein thepredetermined value is substantially between 1% to 5%.
 7. The system ofclaim 1, wherein the control device is further operative to generate anerror signal indicative of a fault condition when the first averagevalue differs from the second average value by the predetermined value.8. The system of claim 1, wherein the control device further comprises avoltage regulator capable of maintaining an output voltage of thegenerator substantially at a regulation voltage.
 9. A method forcontrolling a vehicle electrical system, said system comprising agenerator, said method comprising: (a) generating two or morealternating phase signals via two or more phase windings associated withone or more stators included in the generator; (b) determining a firstand second average values of two of the two or more alternating phasesignals; and (c) at least one of limiting and ceasing a total electricaloutput current of the generator, via a generator output powercontroller, when the first average value differs from the second averagevalue by a predetermined value.
 10. The method of claim 9, furthercomprising: (d) generating an error signal indicative of a faultcondition when the first average value differs from the second averagevalue by the predetermined value.
 11. The method of claim 9, furthercomprising: (d) maintaining an output voltage of the generatorsubstantially at a regulation voltage via a voltage regulator.
 12. Acontrol device for a generator, said generator comprising two or morephase windings associated with one or more stators, said two or morephase windings operative to generate two or more alternating phasesignals, said control device comprising: a processor, including aprogramming code operable on the processor, coupled with the two or morephase windings and a generator output power controller; wherein saidprocessor is configured to: (a) measure the two or more alternatingphase signals, via two or more lines; (b) determine a first and secondaverage values of two of the two or more alternating phase signals; and(c) apply a control signal to the generator output power controller toat least one of limit and cease a total electrical output current of thegenerator, via a control line, when the first average value differs fromthe second average value by a predetermined value.
 13. The controldevice of claim 12, wherein the two or more alternating phase signalscomprise two or more alternating phase voltage signals and wherein eachalternating phase voltage signal is measured between one end of thecorresponding phase winding and one of ground or reference DC.
 13. Thecontrol device of claim 12, wherein the two alternating phase signalsare generated by two different phase windings associated with twodifferent stators.
 14. The control device of claim 12, wherein thegenerator output power controller comprises at least one of a voltageregulator, a field coil, and a semiconductor switch.
 15. The controldevice of claim 12, wherein (b) comprises filtering the two or morealternating phase signals and calculating a first and second DC valuesfrom two of the two or more filtered alternating phase signals.
 16. Thecontrol device of claim 12, wherein the processor is configured to applya phase modulated signal to limit the total electrical output current ofthe generator.
 17. The control device of claim 12, wherein the processoris configured to apply a step signal to cease the total electricaloutput current of the generator.
 18. The control device of claim 12,wherein (c) comprises applying a control signal to the generator outputpower controller to at least one of limit and cease a total electricaloutput current of the generator, via the control line, when a ratiobetween the first and second average values is outside of apredetermined range.
 19. The control device of claim 18, wherein thepredetermined range is substantially between 95% to 105%.
 20. Thecontrol device of claim 12, wherein the processor is further configuredto generate an error signal indicative of a fault condition, via acommunication line, when the first average value differs from the secondaverage value by the predetermined value.
 21. The control device ofclaim 12, wherein the processor is further configured to measure anoutput voltage of the generator, via an output-voltage line, and to varya duty cycle of the generator output power controller, via the controlline, so that the output voltage is substantially equal to a regulationvoltage.
 22. A method for controlling a generator, said generatorcomprising two or more phase windings associated with one or morestators, said two or more phase windings operative to generate two ormore alternating phase signals, said method comprising: (a) measuringthe two or more alternating phase signals, via two or more lines; (b)determining a first and second average values of two of the two or morephase signals; and (c) applying a control signal to a generator outputpower controller to at least one of limit and cease a total electricaloutput current of the generator, via a control line, when the firstaverage value differs from the second average value by a predeterminedvalue.
 23. The method of claim 22, wherein the two or more alternatingphase signals comprise two or more alternating phase voltage signals andwherein (a) comprises measuring the two or more alternating phasevoltage signals between one end of the corresponding phase winding andone of ground or reference DC.
 24. The method of claim 22, wherein (b)comprises filtering the two or more alternating phase signals andcalculating a first and second DC values from two of the two or morefiltered alternating phase signals.
 25. The method of claim 22, wherein(c) comprises applying a phase modulated signal to limit the totalelectrical output current of the generator.
 26. The method of claim 22,wherein (c) comprises applying a step signal to cease the totalelectrical output current of the generator.
 27. The method of claim 22,wherein (c) comprises applying a control signal to the generator outputpower controller to at least one of limit and cease a total electricaloutput current of the generator, via the control line, when a ratiobetween the first and second average values is outside of apredetermined range.
 28. The method of claim 22, further comprising: (d)generating an error signal indicative of a fault condition, via acommunication line, when the first average value differs from the secondaverage value by the predetermined value.
 29. The method of claim 22,further comprising: (d) measuring an output voltage of the generator,via an output-voltage line; and (e) varying a duty cycle of thegenerator output power controller, via the control line, so that theoutput voltage is substantially equal to a regulation voltage.
 30. Acontrol device for a generator, said generator comprising two or morephase windings associated with one or more stators, said two or morephase windings operative to generate two or more alternating phasesignals, said control device comprising: a processor, including aprogramming code operable on the processor, coupled with the two or morephase windings and a generator output power controller; wherein saidprocessor is configured to: (a) measure the two or more alternatingphase signals, via two or more lines; (b) determine a first and secondaverage values of two of the two or more alternating phase signals; and(c) generate an error signal indicative of a fault condition, via acommunication means, when the first average value differs from thesecond average value by a predetermined value.
 31. The control device ofclaim 30, wherein said communication means comprises a communicationterminal, coupled with a computer system, capable oftransmitting/receiving a communication signal indicative of said faultcondition.
 32. The control device of claim 30, wherein saidcommunication means comprises a light emitting diode, generating aflashing light pattern indicative of said fault condition.
 33. A methodfor controlling a generator, said generator comprising two or more phasewindings associated with one or more stators, said two or more phasewindings operative to generate two or more alternating phase signals,said method comprising: (a) measuring the two or more alternating phasesignals, via two or more lines; (b) determining a first and secondaverage values of two of the two or more phase signals; and (c)generating an error signal indicative of a fault condition, via acommunication means, when the first average value differs from thesecond average value by a predetermined value.